Cast piston with hollow core and head cover

ABSTRACT

A cast piston for use in an axial and/or radial hydraulic translating unit, comprising a hollow body portion having inner surfaces defining a cavity interrupted by an angular rib extending from a first end portion of the piston to a second end portion, the rib defining a passage to translate a lubricating fluid through the piston body.

United States Patent 1 1 Hein 1 1 CAST PISTON WITH HOLLOW CORE AND HEAD COVER [75] lnventor: Allyn .lohn l-lein, .loliet, 111.

[73] Assignee: Caterpillar Tractor Company,

Peoria. 111.

[22] Filed: Nov. 23, 1973 [2]] Appl. No.: 418,190

[52] US. Cl. 92/181; 91/488; 92/172 [51] Int. Cl Fl6j 1/08 [58] Field of Search 92/172, 181, 239; 91/488,

[56] References Cited UNITED STATES PATENTS 1.167.975 1/1916 Burlingham 92/172 X May 13, 1975 1,487.965 3/1924 Michell 1. 92/181 X 3.022.901 2/1962 Fisher 1. 92/181 X 3,319,575 5/1967 Havens 91/488 Primary E.\'aminerlrwin C. Cohen Attorney, Agent, or FirmPhillips, Moore. Weissenberger, Lempio & Stabala [57] ABSTRACT 4 Claims, 2 Drawing Figures CAST PISTON WITH HOLLOW CORE AND HEAD COVER BACKGROUND OF THE INVENTION This invention relates to a cast lightweight piston wherein a passage traverses a hollow, elongate cavity within the piston.

Certain well-known hydraulic translating units utilize orbiting pistons to convert mechanical power into hydraulic power and vice versa. These translating units include any one of several well-known means to transform rotational movements into reciprocating movements and vice versa as the pistons orbit around a rotational axis.

Conventionally, in order to reduce the effect of the inertial forces operating on the piston during operation of the hydraulic translating unit, the pistons by various means are hollowed out in the body section. This, however, increases the dead volume of fluid that must be moved within a hydraulic translating unit and has the effect of decreasing the efficiency of those units. Conventionally, certain other such pistons contain various sleeves, fillers and passages which have the undesirable side-effects of structural weakness, cavitation, erosion, noise while operating, and are more complicated and expensive to manufacture, requiring substantial machine work. (See U.S. Pat. No. 3,319,575 to Havens; British Pat. No. 855,582 to Skinner.) Additionally, joining of the component parts often requires multiple welding operations and a substantial number of machining and/or chemical operations which increase the cost of manufacture and often cause structural weakness of the piston.

Of general interest are U.S. Pat. No. 3,l87,644 to Ricketts; U.S. Pat. No. 3,633,467 to Watanabe, et al; and U.S. Pat. No. 3,707,113 to Hein, et al.

SUMMARY AND OBJECTS OF THE INVENTION The object of this invention, therefore, is to provide an effective and easily-manufactured piston with means to operate at high speeds with a minimum of resistance to the lubricating fluid within the hydraulic translating unit, without a filler material or other non-cast device and with high integral strength.

In accordance with such object, this invention provides a hollow-core piston defining a passage extending from the first end portion to the second end portion of the piston. A cast rib defines this passage and improves the structural strength of the piston as well. A stepbored seat defined by the second end portion, and fur ther comprising a cover cap which is piloted into said bore in a sealing relationship with the bore.

BRIEF DESCRIPTION OF THE DRAWINGS Other objects of this invention will become apparent from the following description and accompanying drawings wherein:

FIG. 1 is a longitudinal cross-sectional view of a piston demonstrating the structure of the piston with its hollow, generally cylindrical cavity which defines a cast angular rib which, in turn, describes a hollow passage traversing the piston, and also shown is the steppedbore defined by the second end portion with a piloted cover cap in a sealing relationship with the bore; and

FIG. 2 is a sectional view taken along the lines lIII of FIG. 1.

DETAILED DESCRIPTION With reference to the drawings, a piston 10 comprises generally a hollow, elongate, cylindrical body portion or member 12 and a first end portion 14, and a second end portion 22, said pistons inner surfaces generally defining a cavity 18. The first end portion 14 cooperates with a conventional piston shoe (not shown) for assembly into a hydraulic translating unit, and is integrally connected to the generally cylindrical body portion 12 by means of a tapered portion 16.

The elongate body portion 12 defines a structurally integrated rib 24 which extends generally from the first end portion 14 to the second end portion 22. The rib 24" further defines an elongate passage 20, which extends axially from the spherical first end portion 14 to the opposite second end portion 22. The second end portion 22 defines a stepped-bore seat 28, and a cap 26 may be piloted in the stepped-bore 28 in a sealing relationship therewith in any fashion which provides a permanent, leakproof seal.

An improved design piston configured as above virtually eliminates the need for complicated and expensive machining in the manufacturing process and provides a structurally strong, non-filled, sealed means of converting rotational movements into reciprocating movements, and vice versa, as the pistons orbit around a rotational axis within a hydraulic translating unit. This improved piston eliminates cavitation, erosion and noise often associated with the prior art; reduces the volume of lubricating fluid necessary and avoids undesirable fluctuations in the pressure of the lubricating fluid within the hydraulic translating unit.

What is claimed is:

1. A piston of the type generally used in hydraulic translating units, wherein said piston comprises a body comprising a generally elongate cylindrical body portion, a first end portion having a first face for engaging the piston to the hydraulic translating unit, and a second end portion having a second face and including an opening therethrough, means closing off said opening;

said cylindrical body portion defining a hollow cavity therewithin; said elongate cylindrical body portion defining a rib extending from said first end portion to said second end portion and extending from the cylindrical body portion along its entire length inwardly of the cavity and formed as one piece with the cylindrical body portion whereby a u-shaped cavity is formed;

said rib defining an elongate passage therein longitudinally traversing the cavity from the first face on said first end portion to the second face on said second end portion.

2. The piston of claim I wherein the body further comprises a tapered portion interconnecting the elongate portion and said first end portion.

3. The piston of claim 1 wherein the second end portion opening defines a step-bored seat, and said closing means includes a cover cap positioned in said bore in a sealing relationship therewith.

4. The piston of claim 3 wherein the body further comprises a tapered portion interconnecting the elongate portion and said first end portion. 

1. A piston of the type generally used in hydraulic translating units, wherein said piston comprises a body comprising a generally elongate cylindrical body portion, a first end portion having a first face for engaging the piston to the hydraulic translating unit, and a second end portion having a second face and including an opening therethrough, means closing off said opening; said cylindrical body portion defining a hollow cavity therewithin; said elongate cylindrical body portion defining a rib extending from said first end portion to said second end portion and extending from the cylindrical body portion along its entire length inwardly of the cavity and formed as one piece with the cylindrical body portion whereby a u-shaped cavity is formed; said rib defining an elongate passage therein longitudinally traversing the cavity from the first face on said first end portion to the second face on said second end portion.
 2. The piston of claim 1 wherein the body further comprises a tapered portion interconnecting the elongate portion and said first end portion.
 3. The piston of claim 1 wherein the second end portion opening defines a step-bored seat, and said closing means includes a cover cap positioned in said bore in a sealing relationship therewith.
 4. The piston of claim 3 wherein the body further comprises a tapered portion interconnecting the elongate portion and said first end portion. 